The present invention relates to apparatus and methods for removing deposits from tubular structures. The invention is particularly useful when implemented in a catheter for removing atheroma (e.g., deposits or degenerative accumulations) from blood vessels, and is therefore described below with respect to such catheters.
Fatty deposits accumulated in the coronary or peripheral arteries of a human patient seriously threaten the health of the patient. One method of treating this condition is bypass surgery in which a portion of the affected vessel is replaced by a section of a healthy vessel. Since this treatment involves open surgery, which inherently presents substantial risk to the patient, it is generally used only as a last resort where other treatments are not available.
Various percutaneous coronary intervention (PCI) treatments are currently available to open a narrowed or blocked segment of a blood vessel. One such treatment is balloon angioplasty, in which a balloon catheter is inserted into the body, manipulated to the location where the blockage appears to be, and inflated to expand the lumen and thereby to increase blood flow. A stent may be applied inside the blood vessel to provide support for the vessel in its expanded condition. However, an angioplasty treatment is frequently followed by a subsequent renarrowing of the blood vessel, requiring a repeat angioplasty treatment.
Another treatment in use is an atherectomy procedure, which involves the removal of the atheroma from the affected vessel with a cutting device delivered to the treatment site by a catheter. The known artherectomy treatments, however, are subject to a number of serious risks, including the possibility of a heart attack during the procedure, a closing of the artery necessitating emergency bypass surgery, bleeding caused by damage to the vessel walls, and irregular heart rhythms caused by the trauma to the body. In addition, an atherectomy treatment is very costly and also can lead to early complications.
Another treatment recently proposed is described in US Published Application 2005/0021071A1, published Jan. 27, 2005, in which a scoring structure, e.g. in the form of a separate expandable cage, is carried by an inflatable balloon so as to score the stenotic material when expanded by the balloon in the blood vessel. However, this proposed treatment would also appear to be subject to many of the foregoing risks and drawbacks.